Valve arrangement



July 1, 1947. R. K. SEDGWICK VALVE ARRANGEMENT Filed Dec. 50, 1945 :s shets-sheet 2 mmvro; 62 2; degiyzybcl' y 1947. R. K. SEDGWICK 2,423,120

VALVE ARRANGEMENT Filed Dec. 30, 1943 3 Sheets-Sheet 3 IN VEN TOR.

Patented July 1, 1947 VALVE ARRANGEMENT Robert K. Sedgwick, Chicago,111., assignor to American Steel Foundries, Chicago, 111., a corporationof New Jersey Application December 30, 1943, Serial No. 516,207

Claims. 1

My invention relates, to hydraulic circuits and more particularly to acircuit comprising a preflll valve for an hydraulic press or the like.

My invention comprehends a novel prefill valve operable to supply lowpressure fluid, such as oil, to the press cylinder as the ram movestoward the work to engage the platen therewith, said valve beingoperable to supply high pressure fluid to the press cylinder after theplaten has engaged the work.

The general object of my invention is to design a preflll valve, such asabove described, having a minimum number of manufactured parts andcapable of long life in service.

A further object of my invention is to provide an arrangement in whichthe main valve stem moves to closed position before high pressure fluidis admitted to the press, thus preventing the high pressure fluid frompassing through the valve and into the tank which containsthe reservoirof low pressure fluid.

Another object of my invention is to design a valve in which the valvestem is maintained in closed position until pressure is bled oil fromthe press cylinder preparatory to pulling back the ram from the work,thus preventing shocks to the tank resulting from admission thereto ofsudden violent surges.

In the drawings:

Figure 1 is' a diagram of an hydraulic circuit utilizing my novelpreflll valve.

Figure 2 is a sectional view through the prefill valve, illustrating theparts thereof in detail.

Figure 3 is a sectional view generally comparable to Figure 2 butillustrating a modification of my novel preflll valve.

Figures 4 and 5 are longitudinal sectional views, respectively, of thehigh pressure inlet valve and the holding valve of the circuit shown inFigure 1.

Describing my invention in detail, the press comprises a cylinder, 2 anda. ram 4 reciprocal therewithin, said ram carrying a platen 5 forengagement with the work, as will be clearly understood by those skilledin the art. The ram 4 is hollowed out as at 6 to form a chamberenclosing a hollow tube 8, the chamber 6 being machined at its upper endas at ill to afford a substantially liquid-tight fit with the tube 8.Actuating fluid, such as oil, under pressure is conveyed to the tube 8through the high pressure pipe line l2 connected to an operating valvel4 of conventional design, fluid being conveyed to the valve l4 throughthe supply line l6 which is connected to the pumps i8, i 8 throughconventional check valves 20, 20 and conventional relief valves 2|, 2|.It may be noted that the valve I4 is adapted in its neutral position todirect pressure fluid from the line l6 to the tank 22 through a line i5with a conventional stop cock I I therein, The pumps are driven by amotor I! supported on a tank 2 or reservoir 22 within which is mountedthe prefill valve, generally designated 24, and hereinafter more fullydescribed, said valve communicatin with the cylinder space constitutingthe advance chamber 25 above the ram 4 through a passage 26 in the topof the cylinder 2.

The high pressure line [2 is connected to one end of the prefill valvethrough the high pressure inlet valve 28 of conventional design, and theopposite end of the preflll valve 24 is connected to the high pressurepullback line 30, which is connected through a conventional holdingvalve 32 to the pull back chamber 34 in the cylinder 2 intermediate theends of the ram 4. The pull back line is connected to the operatingvalve l4.

The valve 28, which is shown. in detail in Figure 4, comprises a casing29 with an internal cylindrical bore affording a substantiallyfluid-tight slidable fit for three cylindrical spools 3| of a valve stemhaving a; piston 33 mounted on its lower end and received within acomplementary cylinder 35 in'th'e casing 29. The casing comprises ports31 and 39 connected respectively to the line l2 and the preflll valve24. The port is. connected to a passage 31a in' the casing 23communicating with the cylinder 35. Thus high pressure fluidjn the lineI2 is transmitted to the cylinder 35, thereby acting on the piston 33 toraise the valve stem to its open position against the resistance" of anadjustable spring 4|, whereupon fluidinay'pass from the line I2 and theport 31 to the port 39 and thence to the prefill valve 24 for{purpose-hereinafter described in connection with the operation of thepreflll valve. When the'linei2is' exhausted, as hereinafter described,the springli inoves the valve stem to its closedaccommodating-unrestricted flow of fluid fromthe-pQrtJS to th tank 22through a port in the casing 29, said port 45 being indicated by adotted line in Figure 4.

It may be noted at this point that the function of the holding valve'32-is to maintain a predetermined pressure in the pull back chamber 34,thus holding the ram in elevated position, as seen in Figure l,- untilthe desired pressure is built up within the chamber 6 to move the raminto engagement with the work. The valve 32 is shown in detail in Figure5 and comprises a casing or body 49 with a cylindrical bore 49areceiving a stem or spindle 5i spring pressed to its closed position byan adjustable spring 53.

' The casing 43 comprises a chamber connected by ports 51 and 59,respectively. to the chamber 34 and the line 30, and the casing 49comprises a spiral groove 5| connecting the chamber 55 to a piston area63 on the spindle 5|. Thus pressure within the chamber 34 is transmittedthrough the port 51 to the chamber 55 and thence through the spiralgroove 5| to'act on the piston area 63, thereby urging the stem 5| toits open position, whereupon fluid may flow from the chamber 34- to theline 36 on the advance stroke of the ram 4, as hereinafter described.Upon release of pressure in the chamber 34, the spring 53 moves the stemto its closed position. It will also be understood that pressure in theline 36 on the retraction stroke of the ram 4 is operable to move thestem 5| to its open position, thereby admitting pressure fluid from theline 36 through the port 58, the chamber 55 and the port 51 to thereturn chamber 34.

Referring now to Figure 2 wherein the prefill valve 24 is illustrated indetail, it will be seen that the valve comprisesa body 36 having acylindrical chamber 38 at one end thereof and a cylindrical chamber 46at the opposite end thereof, both chambers communicating with theintervening outlet passage 42 which is connected to the before-mentionedpassage 26 in the top of the cylinder 2, the body 36 of the prefillvalve being secured to the top of said cylinder by means of stud and nutassemblies 43, 43. At each side thereof the body 36 comprises the coredinlet opening 44 for the chamber 38, an inlet opening 46 also beingprovided for the chamber 46, said opening 46 aflording a connection tothe high pressure line I2.

The valve stem 41 is provided at one end thereof with a cylindricalportion ailorded a sliding fit within the chamber 46, the opposite end48 of the stem 41 being a pistonlike member of reduced diameter andextending through the chamber 38 into the cylinder 56 formed within thebody 36. A plurality of piston rings 52, 52 are provided for thepistonlike element 48 of the valve stem.

The larger-diameter portion of the valve stem 41 is provided with a seat54 intermediate the ends of the stem for cooperation with acomplementary seat portion of the body 36 formed at the inner extremityof the chamber 38, and the largerdiameter portion of the stem ishollowed out as at 56 to form a cylindrical chamber within which a ringvalve 58 reciprocates, said ring valve bein operable in its closedposition to close the inner extremities of the ports 66, 66, extendingthrough the valve stem and communicating with the chamber 56therewithin.

The ring valve 58 comprises the ports 62, 62 therethrough aflordingmeans of communication between the stem chamber 66 and the body chamber46, and the ring valve is mounted by means of a nut 64 on a pistonlikespindle 66 which reciprocates within a complementary cylinder 68 in thespindle cap 16, said cap being secured to the body 36 by means of thecap screws 1|, H.

The high pressure pull back line 36, as best seen in Figure 2, isconnected to the cylinder 56 and comprises a branch line 12communicating with the cylinder 68 through the one-way check valve 14. Aby-pass line 16 is connected to the branch 12 at a point intermediatethe valve 14 and the cylinder 68, and said by-pass line communicateswith the cylinder 56 through a port 18 in the body 36.

The manner in which my novel prefill valve functions is best understoodby a description of the operation of the press. Assuming that theoperator desires to engage the platen 5 with the work, high pressurefluid is directed into the line l2 and at the same time pressure in thepull back line 36 is relieved and the same is opened to discharge bymeans of the operating valve I4. This causes pressure to be built upwithin the chamber 6 of the ram through the tube 8, thus causing the ramto move downwardly to engage the platen 5 with the work. Under theseconditions, the stem 41 of the prefill valve 24 is in its open positionwith the seat 54 disengaged from the complementary body seat and withthe ports 66, 66 disposed within the chamber 46. The manner in which thestem 41 is moved to its open position is hereinafter more fullydescribed in connection with the retraction stroke of the ram 4. Thus.fluid is permitted to flow from the tank 22 through the openings 44, 44of the body into the chamber 38 thereof and downwardly through thepassages 42 and 26 into the cylinder space 25 which becomes increasinglylarge as the ram 4 moves downwardly.

When the platen 5 engages the work, the resulting resistance to downwardmovement of the ram 4 causes pressure to be built up within the chamber6 and the high pressure line l2 to a predetermined value at which thehigh pressure inlet valve 28 opens to permit communication between thehigh pressure line I2 and the chamber 46 through the inlet opening 46 ofthe prefill valve. The increasing pressure in the chamber 46 causes thestem 41 to move toward the left to its closed position until its seat 54engages the complementary seat portion of the body 36 to close the innerextremity of the chamber 38, thereby cutting off the tank or reservoir22 from the passa e 42 of the prefill valve.

At this point, pressure builds up against the spindle 66 and the nut 64associated with the ring valve 58, said spindle acting as a smallpiston. At a predetermined pressure, the one-way check valve 14 opens topermit discharge of fluid from the branch 12 into the pull back line 36,thus permitting the ring valve 58 and its spindle 66 to move toward theright to their open position in response to the increasing pressure inthe chambers 46 and 56.

Thus, with the main stem 41 in its closed position and the ring valve 58in its open position, high pressure fluid is permitted to pass throughthe inlet 46 and the chamber 46 through the ports 62, 62 and 66, 66 andinto the passage 42 of the prefill valve from which the high pressurefluid is conveyed to the cylinder space 25 above the ram. This permitsutilization of the full cross-sectional area of the ram in building uppressure against the work.

When it is desired to retract or pullback the platen 5 from engagementwith the work, the high pressure line I2 is opened to discharge, andhigh pressure fluid is directed into the pull back line 36 whichcommunicates with the pull back chamber 34 through the holding valve 32.

Pressure in the pull back line 36 is transmitted to the prefill valvecylinder 56, and as soon as the pressure in the chambers 46 and 56 hasbeen sufficiently exhausted through the line l2, which is now open todischarge, the stem 41 is moved toward the right to its open position.It will be understood that the valve 28, as above described, is adaptedin its closed position to accommodate flow of fluid from the prefillvalve 24 to the tank 22. Thus, when the line I2 is opened to dischargeand pressure fluid is admitted to the pullback line 36 which isconnected to the cylinder 56, the stem 41 may readily move toward theright, as seen in Figure 2, to its open position. In this connection itshould be emphasized that the stem 41 does not move to its open ositionuntil pressure in the chambers 56 and 46 has been exhausted for thereason that the eflective crosssectional area of the larger-diameterportion of the stem 41 is considerably greater than the smaller-diameterportion 48 thereof. By virtue of this arrangement, high pressure fluidis prevented from entering the tank 22 during a pull back operation, andit will be understood by those skilled in the art that this is avaluable feature in that it prevents damage to the tank 22 consequentupon the admission thereto of violent surges.

When the small end 48 of the stem 41 moves to the right, as seen inFigure 2, past the port 10, pressure is transmitted therethrough andthrough the by-pass line I6 and the branch line 12 to the cylinder 68,thus urging the spindle I 66 and the ring valve 60 toward the left intotheir closed position for the next cycle of the press.

It may be noted that when the stem 41 is in its open position, the ports60, 60 are disposed within the chamber 40,'thereby preventing fluid frompassing through the chambers 56 and 40 as the ram moves upwardly withinthe cylinder .2. Thus, the fluid from the cylinder space 25 above theram is forced back into the tank 22 through the passage 42 and thechamber 38 of the prefill valve.

When the platen has been pulled back to its proper retracted position,the stroke control rod (Figure 1), mounted thereon, engages the pivotedoperating member 82 and by a cam action urges said operating member intoengagement with the portion 84 of the operating valve, whereby thelatter is operative in conventional manner to. relieve the pressure inthe pull back line 30, as will be clearly understood by those skilled inthe art.

It will be understood that although the illustrated embodiment of myinvention comprises an arrangement in which the prefill valve is mountedwithin the tank 22 so that the fluid therein may enter the prefill valvethrough the inlet openings 44, 44 in the body 36, if desired, theprefill valve may be disposed in a position exterior of the tank 22 andmay be connected therewith by any suitable fittings associated with theinlet openings 44,44.

Referring now to Figure 3 which illustrates a modification of my novelprefill valve, the body I02 comprises the spaced chambers I04 and I06and the intervening outlet passage I08 communicating therewith. At eachside thereof the chamber I04 is provided with an inlet opening H0 and aninlet passage .I I2 is provided for the chamber I06, said inlet passageII2 being adapted for connection to the high pressure line I2, and theinlet openings 0, H0 being adapted to permit passage of fluid from andto the associated tank.

The stem H4 is substantially identicalwith that described for theprevious embodiment and comprises the pistonlike portion II6 of reduceddiameter at one end thereof for reciprocation within the'cylinder I I0formed in the body I02, said cylinder being connected by means of a portI20 to the pull back line 30, as in the previously described embodiment.

The stem H4 is formed with a cylindrical chamber I22 therein for thereception of the ring valve I24 which isadapted to open and close theports I26, I26 communicating with the stem chamber I22. The ring valveI24 is mounted by means of a nut I28 on the pistonlike spindle I30 whichprojects through an opening I32 in the body I02 for abutment with a coilspring I34 housed within a spring cap I36 secured in any 'ton I38.

It will be understood that the embodiment illustrated in Figure 3 issubstantially identical with that shown in Figure 2 except for the factthat the ring valve I24 is actuated to its closed position by the springI34, whereas, in Figure 2 the ring valve is hydraulically actuated toits closed position. Thus, during the advance stroke of the ram 4aspressure builds up in the prefill valve chamber I06, the stem M4 isurged to its closed position and thereafter, as pressure increases inthe chamber I06, the ring valve I24 is urged to its open position,toward the right as seen in Figure 3, against the resistance of thespring I34. 0n the pull back stroke of the ram, the chamber I06 isexhausted and high pressure fluid is admitted to the cylinder H0 throughthe pull back line 30, thus urging the'stem II4 to its open positionwith the ports I26, I26 disposed within the chamber I06. As soon as thepressure in the chamber I06 has been suiliciently exhausted to permitmovement of the stem II4 to its open position, the ring valve I24 isurged to its closed position by means of the spring I34, and the valveis ready for the next cycle of the press.

It is to be understood that I do notwish to be limited by the exactembodiments'of the device shown which are merely by way of illustrationand not limitation as various and other forms of the device will, ofcourse, be apparent to those skilled in the art without departing fromthe spirit of the inventionor the scope of the claims.

I claim: v

1. In an hydraulic circuit, a prefill valve comprising a body withspaced inlet chambers and an intervening outlet passage communicatingtherewith, a reservoir of low pressure fluid connected to one of saidchambers, a high pressure line connected to the other chamber, a valvestem reciprocal within said last-mentioned chamber and afiorded asliding fit therein, said stem comprising a pistonlike portion of lessdiameter than the first-mentioned chambe and extending therethrough, acylinder associated with said body and receiving the adjacent extremityof said piston like portion, a high pressure line connected to saidcylinder, a chamber in said stem comprising a plurality of portsextending therethrough, a seat on said stem intermediate its ends forcooperation with a complementary seat portion on said body at theadjacent extremity of said first-mentioned chamber for closing the samein the closed position of the stem, said ports being so formed andarranged that they communicate with said passage in the closed positionof the stem and are disposed within said second-mentioned chamber in theopen position of the stem, 2. ring valve with a plurality of portstherethrough, said ring valve being reciprocal within said stem chamberfor opening and closing the inner extremities of said first-mentionedsaid last-mentioned means comprising a port 7 open position of the stem,another cylinder associated with said body and receiving the adjacentextremity of said spindle, a branch line connected to saidlast-mentioned cylinder and connected to said second-mentioned highpressure line through a one-way valve permitting flow oi fluid from saidlast-mentioned cylinder and preventing flow of fluid toward saidlast-mentioned cylinder, and a by-pass line connected to saidlast-mentioned port and connected to said branch line at a pointintermediate said valve and said last-mentioned cylinder,

2. In an hydraulic circuit, a preflll valve comprising a bochr withspaced chamber-san an intervening outlet passage communicatingtherewith, an inlet for one of said chambers connected to a highpressure line, an inlet for the other chamber connected to a source offluid under relatively low pressure, a cylinder stem having one end ofgreater diameter than the other, the large end of said stem beingaiiorded a sliding flt within said first-mentioned chamber and the smallend of said stem being of less diameter than that of saidsecond-mentioned chamber and extending therethrough for reception withina complementary cylinder associated with said body, a high pressure lineconnected to said cylinder, a chamber in the large end of said stem,ports through said stem communicating with said last-mentioned chamber,a seat on said stem intermediate its ends for cooperation with acomplementary seat portion at the adjacent extremity of saidsecond-mentioned chamber for closing the same in the closed position ofthe stem, a ring valve slidingly fitted in said stem chamber, said ringvalve being formed and arranged to close said ports in its closedposition and to uncover said ports in its open position, ports throughsaid ring valve, 9, spindle connected to said ring valve and having anextremity projecting through a complementary opening in the adjacentportion of said body, means cooperating with said extremity for movingsaid ring valve to its closed position when the fluid pressure in saidfirst-mentioned chamber reaches a predetermined low level, and means foralternately admitting pressure to and relieving the pressure inrespective fines, said first-mentioned means comprising a spring capassociated with said body, a spring mounted within said cap and bearinagainst said spindle, and means projecting externally of said cap foradjustably compressing said spring against said spindle.

3. In an hydraulic circuit, a preflll valve comprising a body withspaced chambers and an intervening outlet passage communicatingtherewith, an inlet for one of said chambers connected to a highpressure line, an inlet for the other chamber connected to a source offluid under relatively low Pressure, a cylindrical stem having one endof greaterdiameter than the other, the large end of said stem beingafiorded a sliding flt within said first-mentioned chamber and the smallend of said stem being of less diameter than that of saidsecond-mentioned chamber and extending therethrough for reception withina complementary cylinder associated with said body, a high pressure lineconnected 8 to said cylinder, a chamber in the large end of said stem,ports through said stem communicating with said last-mentioned chamber,a seat on said stem intermediate its ends for cooperation with acomplementary seat portion at the adjacent extremity of saidsecond-mentioned chamber for closing the same in the closed position ofthe stem, 9. ring valve slidingly fitted in said stem chamber, said ringvalve being formed and arranged to close said ports in its closedposition and to uncover said ports in its open position, ports throughsaid ring valve, a spindle conn cted to said ring valve and having anextm ity projecting through a complementary opening in the adjacentportion of said body, means cooperating with said extremity for movingsaid ring valve to its closed position when the fluid pressure insaidfirst-mentioned chamber reaches a predetermined low level, means foralternately admitting pressure to and discharging pressure in respectivelines, said first-mentioned means comprising another cylinder associatedwith said body and receiving the adjacent extremity of said spindle, andmeans for conveying high pressure fluid to said last-mentioned cylinder.

4. In an hydraulic circuit, a prefill valve comprising a body withspaced inlet chambers and an intervening outlet passage communicatingtherewith, a reservoir of low pressure fluid connected to one of saidchambers, a high pressure line connected to the other chamber, a valvestem reciprocal within said last-mentioned chamber and afforded asliding fit therein, said stem comprising a pistonlike portion of lessdiameter than the first-mentioned chamber and extending therethrough, acylinder associated with said body and receiving the adjacent extremityof said pistonlike portion, a high pressure line connected to saidcylinder, a chamber in said stem comprising a plurality of portsextending therethrough, a seat on said stem intermediate its ends forcooperation with a. complementary seat portion on said body at theadjacent extremity of said first-mentioned chamber for closing the samein the closed position of the stem, said ports being so formed andarranged that they communicate with said passage in the closed positionof the stem and are disposed within said secondmentioned chamber in theopen position of the stem, a ring valve with a plurality of portstherethrough, said ring valve being reciprocal within said stem chamberfor opening and closing the inner extremities of said first-mentionedports in the open and closed positions respectively of said ring valve,a pistonlike spindle connected to said ring valve and extending througha complementary opening in an adjacent wall of said body, means foralternately admitting pressure to respective of said high pressurelines, and means associated with said spindle for moving said ring valveto its closed Position when the pressure in said first-mentioned line isrelieved, said last-mentioned means comprising a spring bearing againstsaid spindle.

5. In an hydraulic circuit, a prefill valve comprising a body withspaced inlet chambers and an intervening outlet passage communicatingtherewith, a reservoir of low pressure fluid connected to one of saidchambers, a high pressure line connected to the other chamber, a valvestem reciprocal within said last-mentioned chamber and afforded asliding fit therein, said stem comprisirg a pistonlike portion of lessdiameter than the first-mentioned chamber and extending therethrough, acylinder associated with said body and receiving the adjacent extremityof said piston-like portion, a. high pressure line connected to saidcylinder, a chamber in said stem comprising a plurality of portsextending therethrough, a seat on said stem intermediate its ends forcooperation with a complementary seat portion on said body at theadjacent extremity of said first-mentioned chamher for closing the samein the closed position of the stem, said ports being so formed andarranged that they communicate with said passage in the closed positionof the stem and are disposed within said second-mentioned chamber in theopen position of the stem, a ring valve with a plurality of portstherethrough, said, ring valve being reciprocal within said stem chamberfor opening and closing the inner extremities of said first-mentionedports in the open and closed positions respectively of said ring valve,a pistonlike spindle connected to said ring valve and extending througha complementary opening in an adjacent wall of said body, means foralternately admitting pressure to respective of said high pressurelines, and means associated with said spindle for moving said ring valveto its closed position when the pressure, in said first-mentioned lineis relieved.

6. In a prefill valve, a body comprising spaced chambers and anintermediate'outlet passage, an inlet opening communicating with eachchamber, a stem having an end of relatively large diameter slidablyfitted within one of said chambers and an end of relatively smalldiameter, said last-mentioned end being of less diameter than that ofthe other chamber and extending therethrough for reception within acomplemen tary cylinder associated with said body, an inlet for saidcylinder, a seat on said stem intermediate its ends for cooperation witha complementary seat portion on said body at-the inner extremity of saidother chamber for closing the same, a chamber formed in the large end ofsaid stem, ports through said large end communieating with saidlast-mentioned chamber, said ports being so formed and arranged as to bedisposed within said passage when said seat is in engagement with saidseat portion and to be disposed within said first-mentioned chambercooperation with a complementary seat portion on said body at the innerextremity of said other chamber for closing the same, a chamber formedin the large end of said stem, ports through said large endcommunicating with said last-mentioned chamber, said ports being soformed and arranged as to be disposed within said passage when said seatis in engagement with said seat portion and to be disposed within saidfirst-mentioned chamber when said seat. is out of engagement with saidseat portion, a ring valve reciprocal within said stem chamber foropening and closing said ports, ports through said ring valve, a spindleconnected to said ring valve and reciprocal within a complementaryopening through said body, and means for moving said spindle and ringvalve inwardly with respect to said stem chamber for closing saidfirst-mentioned ports when the fluid pressure in said stem chamberreaches a predetermined low level, said means comprising a springbearing against said spindle.

8. In a prefill valve, a body comprising spaced chambers and anintermediate outlet passage, an inlet opening communicating with eachchamber, a stem having an end of relatively large diameter slidablyfitted within one of said chambers and an end of relatively smalldiameter, said last-mentioned endbeing of less diameter than that of theother chamber and extending therethrough for reception within acomplementary cylinder associated with said body, an inlet for saidcylinder, a seat on said stem intermediate its ends for cooperation witha complementary seat portion on said body at the inner extremity of saidother chamber for closing the same, a chamber formed in the large end ofsaid stem, ports through said large end communicating with saidlast-mentioned chamber, said ports being so formed and arranged as to bedisposed within said passage when said seat is in engagement with saidseat portion and to be disposed within said first-mentioned chamber whensaid seat is out of engagement with said seat portion, a ring valvereciprocal "within said stem chamber for openin and closing said ports,ports through said ring valve, a spindle connected to said ring valveand reciprocal within a complementary opening through said body, andmeans for moving said when said seat is out of engagement with said seatportion, a ring valve reciprocal within said stem chamber for openingand closing said ports, ports through said ring valve, a spindleconnected to said ring valve and reciprocal within a complementaryopening through said body, means for moving said spindle and ring valveinwardly with respect to said stem chamber for closing saidfirst-mentioned ports when the fluid pressure in said stem chamberreaches a predetermined low level, said means comprising anothercylinder associated with said body andreceiving the adjacent extremityof said spindle,

spindle and ring valve inwardly with respect to said stem chamber forclosing said first-mentioned ports when the fluid pressure in said stemchamber reaches a predetermined low level.

9. In a valve, a body having spaced chambers and an intervening passagecommunicating therewith, inlets communicating with respective chambers,a stem reciprocal within one of said chambers and comprising means forclosing the other of said chambers from communication with said passagein the closed position of the stem, a chamber in said stem, a portthrough said stem communicating with said stem chamber, said port beinformed and arranged to be disposed within said passage in the closedposition of the stem and to be disposed within said first-mentionedchamber in the open position of the stem, a valve member reciprocalwithin said stem chamber and formed and arranged to open andclose saidport in the open and closed positions respectively of said valve member,a port through said valve member connecting said one chamber with saidstem chamber, actuating means for moving said stem to open position,said actuating means comprising a pistoniike portion on said stem ofless cross-sectional area than that of said other chama seat on saidstem intermediate its ends for her and extending therethrough, a fluidcylinder associated with said body. said piston-like portion beingslidably fitted within said cylinder, and means for admitting pressurefluid to said cylinder, and actuating means for moving said valve.member to its closed position, said lastmentioned means comprising aspindle connected to said valve member and extending into acomplementary opening in said body, and operating means for saidspindle.

10; In an hydraulic circuit for an hydraulic motor comprising a cylindermeans including advance and return chambers and ram means reciprocaltherein; the combination of a prefill valve including a body having apassage communicating with said advance chamber, said body comprising ahigh pressure fluid chamber and a low pressure fluid chambercommunicating with said passage, a valve stem slidably fitted in thehigh pressure fluid chamber and comprising means for closing the lowpressure fluid chamber from communication with said passage in theclosed position of said stem, means for urging said stem to its openposition comprising a cylinder associated with said body and receiving aportion of said stem, a chamber in said stem communicating with saidhigh pressure chamber, a port through said stem communicating with thechamber therein and adapted to communicate with said passage in theclosed position only of said stem, a valve member in said stem chamberfor opening and closing said port, a port through said valve memberpermitting flow of fluid between said stem chamber and said highpressure chamber, said valve member comprising a pistonlike elementslidably fitted within a complementary opening in said body, a source oflow pressure fluid connected to said low pressure 12 chamber, a highpressure line connected to said high pressure chamber, a high pressureline connected to said return chamber and to said secondmentionedcylinder, means for alternately admitting pressure fluid to anddischarging pressure fluid in respective lines, and actuating meansassociated with said element for moving said valve member to its closedposition, said actuating means comprising a cylinder associated withsaid body and receiving said element, a connection between saidsecond-mentioned line and said lastmentioned cylinder, saidlast-mentioned connection comprising a one-way check valve accommodatingflow of fluid from said last-mentioned cylinder and preventing flow offluid toward said last-mentioned cylinder, and a by-pass line connectingsaid second-mentioned cylinder with said last-mentioned cylinder,

ROBERT K. SEDGWICK.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 897,047 Astfalck Aug. 25,19081,851,622 Ernst Mar. 29, 1932 30 2,114,005 Tyler Apr. 12, 1938 2,244,420Dinzl June 3, 1941 2,152,870 Cannon Apr. 4, 1939 FOREIGN PATENTS 35Number Country Date 237,661 Great Britain 1925 436,431 Great Britain1935

